For example for forklift trucks, various lifting apparatuses are known by means of which the load-bearing forks can be lifted or lowered and which have, for example, a plurality of extendable supporting masts. These supporting masts, which can be extended and retracted telescopically and have either profiled mounts or piston/cylinder units, essentially function by a pressure medium being applied to them, the forks being actuated in a known manner by means of a chain assembly. The height of the loads which can be stacked on is in each case dependent on the design of the forklift truck. The lowermost fork position is essentially designed such that the undersides of the forks can rest directly on the flat ground or can be moved so as to rest on the flat ground.
It often arises in practice that, for example owing to wear on the tire profile of the forklift truck tires, the forks are lowered so far downwards that either sections of the underside of the forks or the entire underside of the forks drag on the floor when the forklift truck is in motion. This results not only in the floor on which the forks are dragging being damaged but also in, over time, the forks themselves being worn or damaged and the entire stroke limitation mechanism being negatively impaired or damaged by the influence of impacts. In such a case, the worn forks need to be replaced, which under some circumstances can be very expensive.
In order to avoid this, it is proposed to provide an assembly for adjusting the lowermost fork position. For this purpose, for example, utility model G-U-84 37 887 proposes an adjustable stop assembly used for stroke limitation for a piston/cylinder unit which has a clamping ring, which can be displaced axially on the piston rod, can be fixed in clamping fashion and has a threaded section in a region of its outer circumference, and a threaded ring, which can be screwed onto the threaded section of the clamping ring and whose front edge facing the cylinder is used as a stop on the cylinder. By adjusting (screwing) the threaded ring in relation to the clamping ring, the lower front edge which is used as the stop on the cylinder of the piston/cylinder unit can be set in a relatively simple manner.
A conventional forklift truck having a lifting apparatus having a piston/cylinder unit can be retrofitted, for example, with such an adjustable stop assembly. For this purpose, the lifting apparatus needs to be disassembled to such an extent that the piston rod is removed from the corresponding cylinder and exposed in order that, first, the clamping ring can be pushed onto the piston rod and, subsequently, fixed in clamping fashion to the piston rod. Then, the threaded ring is pushed onto the piston rod and screwed onto the outer threaded section of the clamping ring before the lifting apparatus can be fitted again. Retrofitting a piston/cylinder unit of a forklift truck with an adjustable stop assembly used for stroke limitation in accordance with this prior art requires, owing to the disassembly/fitting of the lifting apparatus having the forks, a large amount of operational downtime, in which the forklift trucks cannot be used, as a result of which the retrofitting is overall cost-intensive.